13,776 research outputs found
Asteroseismology of DAV white dwarf stars and G29-38
Asteroseismology is a powerful tool to detect the inner structure of stars.
It is also widely used to study white dwarfs. In this paper, we discuss the
asteroseismology work of DAV stars. The detailed period to period fitting
method is fully discussed, including the reliability to detect the inner
structure of DAV stars. If we assume that all observed modes of some DAV star
are the = 1 ones, the errors of model fitting will be always great. If we
assume that the observed modes are composed of = 1 and 2 modes, the errors
of model fitting will be small. However, there will be modes identified as
= 2 without quintuplets observed. G29-38 has been observed spectroscopically
and photometrically for many years. Thompson et al. (2008) made
identifications for the star through limb darkening effect. With eleven known
modes, we also do the asteroseismology work for G29-38, which reduces the
blind fittings and is a fair choice. Unfortunately, our two best-fitting
models are not in line with the previous atmospheric results. Based on factors
of only a few modes observed, stability and identification of eigenmodes,
identification of spherical degrees, construction of physical and realistic
models and so on, detecting the inner structure of DAV stars by
asteroseismology needs further development.Comment: 7pages, 1figur
Linear complexity of generalized cyclotomic sequences of order 4 over F_l
Generalized cyclotomic sequences of period pq have several desirable
randomness properties if the two primes p and q are chosen properly. In
particular,Ding deduced the exact formulas for the autocorrelation and the
linear complexity of these sequences of order 2. In this paper, we consider the
generalized sequences of order 4. Under certain conditions, the linear
complexity of these sequences of order 4 is developed over a finite field F_l.
Results show that in many cases they have high linear complexity.Comment: Since there is a crucial error in Theorem 1 in the first version, we
replace it by the new on
Scheme for conditional generation of photon-added coherent state and optical entangled state
We propose a simple scheme to generate an arbitrary photon-added coherent
state of a travelling optical field by using only a set of degenerate
parametric amplifiers and single-photon detectors. Particularly, when the
single-photon-added coherent state (SPACS) is observed by following, e.g., the
novel technique of Zavatta \emph{} (Science 306, 660 (2004)), we also
obtain the generalized optical entangled state. Finally, a qualitative
analysis of possible losses in our scheme is given.Comment: 8 pages, 3 figure
Automatic trajectory measurement of large numbers of crowded objects
Complex motion patterns of natural systems, such as fish schools, bird
flocks, and cell groups, have attracted great attention from scientists for
years. Trajectory measurement of individuals is vital for quantitative and
high-throughput study of their collective behaviors. However, such data are
rare mainly due to the challenges of detection and tracking of large numbers of
objects with similar visual features and frequent occlusions. We present an
automatic and effective framework to measure trajectories of large numbers of
crowded oval-shaped objects, such as fish and cells. We first use a novel dual
ellipse locator to detect the coarse position of each individual and then
propose a variance minimization active contour method to obtain the optimal
segmentation results. For tracking, cost matrix of assignment between
consecutive frames is trainable via a random forest classifier with many
spatial, texture, and shape features. The optimal trajectories are found for
the whole image sequence by solving two linear assignment problems. We evaluate
the proposed method on many challenging data sets
Simultaneous creations of discrete-variable entangle state and single-photon-added coherent state
The single-photon-added coherent state (SPACS), as an intermediate
classical-to-purely-quantum state, was first realized recently by Zavatta
\emph{} (Science 306, 660 (2004)). We show here that the success
probability of their SPACS generation can be enhanced by a simple method which
leads to simultaneous creations of a discrete-variable entangled state and a
SPACS or even a hybrid-variable entangled SPACS in two different channels. The
impacts of the input thermal noise are also analyzed.Comment: 6 pages, 1 figur
Correlation Measurement of an unknown state with Weak Coupling
Traditionally, quantum state correlation can be obtained with calculations on
a state density matrix already known. Here, we propose a model with which
correlations of unknown quantum states can be obtained. There are no needs of
classical communication in the course of coupling, optimization and complicated
calculations. All we need are weak coupling and ancillary systems. We detail
the model on the state in which particles belong to the different owners. A
concisely example is elaborated in the last part of this paper
Pseudorapidity dependent hydrodynamic response in heavy-ion collisions
We propose a differential hydrodynamic response relation, , to describe the formation of a
pseudorapidity dependent elliptic flow in heavy-ion collisions, in response to
a fluctuating three-dimensional initial density profile. By analyzing the
medium expansion using event-by-event simulations of 3+1D MUSIC, with initial
conditions generated via the AMPT model, the differential response relation is
verified. Given the response relation, we are able to separate the two-point
correlation of elliptic flow in pseudorapidity into fluid response and
two-point correlation of initial eccentricity. The fluid response contains
information of the speed of sound and shear viscosity of the medium. From the
pseudorapidity dependent response relation, a finite radius of convergence of
hydrodynamic gradient expansion is obtained with respect to realistic fluids in
heavy-ion collisions.Comment: The published version, 7 pages, 5 figure
Longitudinal fluid response and pseudorapidity dependent flow in relativistic heavy-ion collisions
We study the pseudorapidity dependent hydrodynamic response in heavy-ion
collisions. A differential hydrodynamic relation is obtained for elliptic flow.
Using event-by-event simulations of 3+1D MUSIC, with initial conditions
generated via a multi-phase transport (AMPT) model, the differential response
relation is verified. Based on the response relation, we find that the
two-point correlation of elliptic flow in pseudorapidity are separated into the
fluid response and the two-point correlation of initial eccentricity.Comment: 4 pages, 2 figures, Quark Matter 2019 proceedin
Long-term Optical Observations of the Be/X-ray Binary X Per
We present the optical spectroscopic observations of X Per from 1999 to 2013
with the 2.16m telescope at Xinglong Station and the 2.4m telescope at Lijiang
station, National Astronomical Observatories of China. Combining with the
public optical photometric data, we find certain epochs of anti-correlations
between the optical brightness and the intensity of the H{\alpha} and HeI 6678
lines, which may be attributed to the mass ejections from the Be star.
Alternative explanations are however also possible. The variability of FeII
6317 line in the spectra of X Per might be also caused by the shocked waves
formed after the mass ejections from the Be star. The X-ray activities of the
system might also be connected with the mass ejection events from the Be star.
When the ejected materials were transported from the surface of the Be star to
the orbit of neutron star, an X-ray flare could be observed in its X-ray light
curves. We use the neutron star as a probe to constrain the motion of the
ejected material in the circumstellar disk. With the diffusion time of the
ejected material from the surface of Be star to the orbit of neutron star, the
viscosity parameter {\alpha} of the circumstellar disk is estimated to be 0.39
and 0.28 for the different time, indicating that the disk around Be star may be
truncated by the neutron star at the 2:1 resonance radius and Type I X-ray
outburst is unlikely to be observed in X Per.Comment: 24 pages, 5 figure, 1 tabl
On (strong) proper vertex-connection of graphs
A path in a vertex-colored graph is a {\it vertex-proper path} if any two
internal adjacent vertices differ in color. A vertex-colored graph is {\it
proper vertex -connected} if any two vertices of the graph are connected by
disjoint vertex-proper paths of the graph. For a -connected graph ,
the {\it proper vertex -connection number} of , denoted by ,
is defined as the smallest number of colors required to make proper vertex
-connected. A vertex-colored graph is {\it strong proper vertex-connected},
if for any two vertices of the graph, there exists a vertex-proper
- geodesic. For a connected graph , the {\it strong proper
vertex-connection number} of , denoted by , is the smallest number
of colors required to make strong proper vertex-connected. These concepts
are inspired by the concepts of rainbow vertex -connection number
, strong rainbow vertex-connection number , and proper
-connection number of a -connected graph . Firstly, we
determine the value of for general graphs and for some
specific graphs. We also compare the values of and . Then,
sharp bounds of are given for a connected graph of order ,
that is, . Moreover, we characterize the graphs of order
such that , respectively. Finally, we study the
relationship among the three vertex-coloring parameters, namely, $spvc(G), \
srvc(G)\chi(G)G$.Comment: 12 page
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